U.S. Pat. No. 4,086,384 describes a highly useful paper-microfoam sheet packaging material in which a layer of a sealed cell microporous foam polymer, such as microfoam, is adhered to a layer of kraft paper, which may be reinforced by fiberglass strands. Such material forms highly effective packages, but does not sufficiently protect moisture-sensitive objects, such as tin plate, which are subject to corrosion under ordinary atmospheric conditions. An object of this invention is to provide a laminated sheet material for packaging a moisture-sensitive material and protecting it from being damaged by moisture over extended periods of storage. Another object is to provide such a laminated sheet material which is suitable for packaging sheets of tin-plated steel or other metals and preventing them from rusting or corroding over extended periods of storage.